As is well known in the art, delivery of pharmacological agents (or drugs) to a specific organ or tissue can be achieved through systemic or local administration. In systemic administration, the agent is introduced into the systemic, or general, circulation by ingestion, injection, inhalation or transdermal administration. Circulating blood delivers the agent to the target tissue by either passive or active transport.
Advantages of systemic administration are that this mode of administration, especially by ingestion, is simple and well accepted by the patient. A disadvantage, however, is that the agent must be administered at relatively high doses in order to reach the target area in sufficient quantity. Moreover, the agent is delivered to the entire body, which can include sites where the agent can cause significant side effects. This is especially true for chemotherapeutic agents that tend to present significant systemic toxicity, and steroids, which present significant long-term systemic side effects.
Another significant disadvantage of systemic administration is that transfer of many pharmacological agents from the blood to certain tissues, such as the brain or an eye, is very inefficient.
An alternative to systemic administration is to administer the pharmacological agent(s) into a target organ (or tissue) or in close proximity thereto. However, as is well known in the art, local administration of an agent into or proximate an organ; particularly, an eye, typically requires strict adherence to numerous safeguards.
As discussed in detail herein, the eye is a delicate sense organ that is surrounded by specialized structures and protected by the orbit bones, soft tissues and eyelids. The eye itself is composed of three primary layers: the sclera, the uvea, and the retina. The iris, ciliary body and choroid constitute the uvea.
Because of the complex nature of the eye, it is susceptible to a large number of abnormalities (and/or diseases). The abnormalities include dry eye, allergies, infections, various inflammatory diseases and glaucoma.
Treatments of the abnormalities and diseases have, in general, been limited to topical administration of agents or preparations. A conventional example of topical administration of an agent to the eye is the delivery of timolol via eye drops.
As is well known in the art, eye drops facilitate transmission of the agent directly to the anterior part of the eye by instillation into the cul-de-sac. The agents are then moved via the tears of the eye across the cornea and sclera into the anterior and posterior chambers of the eye without initially entering the systemic circulation path.
The advantage of this mode of administration (or delivery) is that the agent is concentrated in the target tissue with a much lower systemic exposure. This tends to reduce the above-mentioned systemic effects.
A disadvantage of this mode of administration is that not all eye tissues are accessible by this route of delivery. Tears can also redirect a significant portion of the agent away from the target area relatively quickly.
A further disadvantage of this mode of administration is that it is mostly applicable to small molecular weight pharmacological agents. Indeed, large molecular weight agents, such as antibodies, are known to diffuse poorly across the conjunctiva.
As is well known in the art, subconjunctival delivery of therapeutic agents is currently performed using a conventional needle and syringe, i.e. subconjunctival injection. As is also well known in the art, this method requires highly skilled and trained personnel and present many risk associated with it. Risks include needle injury to the patient and the practitioner, as well as risks associated with disposal of the needle.
Recently, intraocular injection using needleless jet injection has been employed to administer agents to the eye. Illustrative are the methods and systems disclosed in U.S. Pat. Pub. Nos. 2004/0210188, 2007/0052139, 2007/0055199, 2007/0055200, 2007/0055214, 20090118738, WO2007058966. However, the disclosed method and systems are only compatible with deep intravitreal injection and do not include injection in the outermost layers of the eye, particularly subconjunctival injection. A major disadvantage is that the high pressures involved for the liquid jet to go through the outer membrane of the eye and into the vitreous compartment is the associated risk of retinal detachment.
Associated with the development of new pharmacological treatments for ocular diseases, specialists are being faced with the responsibility for meeting the ever increasing demand for subconjunctival administration of pharmacological agents and, hence, addressing the aforementioned issues associated with the prior art subcutaneous injection methods and systems. There is also no universally accepted standard process for performing a subconjunctival injection.
Further, subconjunctival injections cannot always be scheduled in advance and each injection requires several steps to prepare the eye and safely perform the injection. The time required to perform injections can thus disrupt office schedules, resulting in unexpected prolongation of patient waiting times.
Therefore, a method and device to standardize and simplify the subconjunctival agent delivery process, improve patient comfort and safety, and increase efficiency of the process is desired.
It is therefore an object of the present invention to provide a subconjunctival agent delivery method and system that provides safe, accurate, consistent, and rapid delivery of therapeutic agents into the subconjunctival space or compartment of the eye.
It is another object of the present invention to provide a subconjunctival agent delivery method and system that facilitates delivery of therapeutic agents into the subconjunctival compartment of the eye with minimal risk of trauma to the patient's eye by the delivery system.
It is another object of the present invention to provide a subconjunctival agent delivery method and system that facilitates delivery of therapeutic agents into the subconjunctival, subtenon spaces or intrascleral and subchoroidal space of the eye.
It is another object of the present invention to provide a subconjunctival agent delivery method and system that facilitates delivery of therapeutic agents into the subconjunctival compartment of the eye with minimal risk of trauma and infection.
It is another object of the present invention to provide a subconjunctival agent delivery method and system that provides semi-automated delivery of therapeutic agents into the subconjunctival compartment of the eye.